Police want to question a pair of reputed Russian mobsters – already under indictment for the killing of a Brooklyn boxer – about the murder of an off-duty cop, The Post has learned.

Police and federal investigators believe Alexander Nosov and Natan Gozman might have been involved in the murder of NYPD Officer Ralph Dols, who was gunned down execution-style outside of his Sheepshead Bay home on Aug. 25, 1997.

Both men are allegedly members of the vicious international organized crime ring Bratva, Russian for “good fellows,” and both have been indicted for the 1995 murder of boxer Sergei Kobozev.

Nosov, 24, aka “Sasha Dlinni” – Russian slang for well-endowed – is currently being held on unrelated charges in Germany and is awaiting extradition to the U.S.. Gozman, who’s in his mid-20s, is still at large.

Sources said while Nosov was out of the country at the time of Dols’ murder, he may have helped plan the hit. Investigators aren’t sure where Gozman was at the time of the murder, but since both he and Nosov operated primarily out of Sheepshead Bay, they want to find out.

Investigators have questioned the informer who fingered Nosov and Gozman to the FBI in the Kobozev case, but he “wasn’t very forthcoming,” one source said. “He knew more than he was saying.”

The probers are also focusing on other members of the Russian mob, and have been stepping up raids on their hangouts in a bid to dig up information on the Dols case, the sources said.

The FBI and NYPD detectives are working together on the investigation, and have put together two theories as to why was he killed:

* He was working for the Russian mob selling steroids – and was skimming from the profits.

* The Russian mob carried out the hit to curry favor with the Mafia. Dols was married to Kimberly Kennaugh, who’d dated one member of Columbo crime family and the widow of another.

Federal investigators have said that currying favor was the reason Nosov and Gozman murdered Kobozev.